Comparison of single daily dose of methimazole and propylthiouracil in the treatment of Graves' hyperthyroidism

OBJECTIVE The present study was to compare the efficacy of a single daily dose of methimazole (MMI) and propylthiouracil (PTU) in the treatment of Graves' hyperthyroidism. BACKGROUND Antithyroid drugs, MMI and PTU, are widely used in the treatment of hyperthyroidism. Previous studies in the treatment of hyperthyroidism with a single daily dose of antithyroid drugs have demonstrated a more favourable result with MMI. However, the efficacy of a single daily dose of PTU was inconsistent. In this study, we examined the therapeutic efficacy of single daily doses of MMI and PTU on the change of thyroid hormones and thyrotropin receptor antibodies (TRAb) levels. METHODS Thirty patients with newly diagnosed Graves' hyperthyroidism were randomly divided into two groups, each receiving a single dose of either 15 mg MMI or 150 mg PTU daily for 12 weeks. The therapeutic efficacy was determined by serum total triiodothyronine (TT3), total thyroxine (TT4), thyrotropin (TSH), free thyroxine (FT4), and TRAb levels at baseline and at the end of 4, 8 and 12 weeks during the study period. RESULTS There was no significant difference in baseline thyroid function parameters. Serum TT3, TT4 and FT4 levels in the MMI-treated group were significantly lower than those of the PTU-treated group after 4 weeks and through the end of the study. MMI also has superior effect on reducing serum TRAb levels than PTU after 8 weeks and at the end of the study. CONCLUSION During the 12-week treatment of Graves' hyperthyroidism, a single daily dose of 15 mg MMI was much more effective in the induction of euthyroidism than a single daily dose of 150 mg PTU. In the doses used in this study, MMI is preferable to PTU when a once-daily regimen of antithyroid drug is considered for the treatment of Graves' hyperthyroidism.